A telephone subscriber line works over a single pair of copper wires installed between Telekom Serbia and the destination. Traditional telephone networks use the basic range to convey voice communications between callers. Given that the use of copper wires allows covering a wider frequency range, ADSL uses a frequency range that is divided into two or more different ranges.
Special filters called splitters separate baseband (the frequency range from 0–4kHz used for transmission of the low frequencies associated with voice traffic) from the frequency range used for data transfer.
ADSL uses two pieces of equipment:
- On the customer end: Frequency divider and an ADSL transceiver (ADSL modem).
A splitter divides the signal into two parts, allowing the voice to go through. It is connected to a standard phone or an ISDN terminal device (ISDN telephone, ISDN fax group 4), depending on whether ADSL works over a regular telephone line or an ISDN BRI port.
When an ADSL transceiver is connected to the other splitter port, it allows data transfer between the client computer/network and an ADSL line. Depending on the manufacturer, it may be possible to integrate a network router/switch or other equipment into an ADSL transceiver.
- At the Internet service provider: DSL Access Multiplexer (DSLAM)
The Digital Subscriber Line Access Multiplexer (DSLAM) consists of a splitter and an ADSL transceiver. At the splitter the traffic is divided into two separate signals – telephone traffic is directed to Telekom Serbia, while the ADSL transceiver provides routing of digital data to the Internet.
The DSLAM provides one of the main differences between user service through ADSL and through cable modems. Cable modem users share a network loop that runs through a neighborhood, which is why adding users often means lowering performance.
With DSLAM, users won't experience a performance decrease as new users are added, until the total number of users begins to saturate the connection to the Internet, which can be easily solved by making an upgrade by the service provider.
ADSL requirements
ADSL requires that copper phone lines be electrically clean. If the client is using a PCM phone line, or a multiparty (Shared Service) line, Telekom Serbia must first provide that a pair of copper wires runs to user's home. (The telephone company wires from a customer to the telephone company's central office.) It is necessary thet the user's phone central supports DSLAM, since the maximum distance up to which ADSL connection is possible over copper cables of adequate diameter is 5–6 km from the nearest telephone exchange.
ADSL use and advantages
By analyzing the needs of small businesses and home users (SOHO), it was noted that it was not always necessary to provide symmetrical data transfer. In fact, such users have significantly more data received than sent.
ADSL is designed as an asymmetric digital transmission system enabling simultaneous transmission of analog (i.e. voice calls) and digital data (via permanent high-speed connection to the Internet) – all that through a single analog telephone line.
ADSL advantages are many and include:
- Permanent connection to the Internet at an affordable price; requires a computer with a free USB port or a built-in network (Ethernet) card
- Wide selection of available ADSL packs with different up and down speeds
- Installation using the existing phone lines and home installations; the existing telephone line retains its primary function for making phone calls
- May be installed regardless of the type of telephone service (analog telephone line, ISDN line, etc.); requires user to be located in the covered area
- When ADSL uses the existing ISDN line, both ADSL channels and the ADSL line are simultenously available to the user
- Wide range of available ADSL equipment at an affordable price
- User retains their existing phone number if their copper phone line is electrically clean
Top reasons for choosing ADSL
- Allows simultaneous use of telephone and internet services
- Eliminates telephone costs for using the Internet (user pays a fixed monthly fee)
- User is informed about the monthly cost in advance, prior to using the service
- Natural and legal entities are subject to the same price and conditions of use
- Enables high-speed data transfer
- Eliminates the need to establish the connection as user is always online; virtually no connection breaks (as different to modem-based connections)
- Provides significantly faster Internet access
- Provided all technical requirements are fulfilled, ADSL installation is a very fast and simple process without the need for setting up additional cables
- Permanent Internet access also implies the possibility of using all Internet services (WEB, MAIL, FTP, CHAT, ICQ, etc.) without limitation
- Supports faster and safer sending of email attachments & larger files via messenger (ICQ, Windows Messenger, MSN Messenger, etc.)
- Allows fast and simple switching to another ADSL pack
ADSL allows fast and efficient use of all Internet services.
